Epidemiologic studies demonstrate that the oral cavity of human adults is relatively resistant to HIV infection, and a number of soluble factors present in saliva have been postulated to confer this protection. In contrast, oral infection of infants who are breast fed by HIV-infected mothers is quite common, suggesting that there are age dependent differences in oral resistance to lentiviruses. We will investigate the basis of these age-dependent differences in antiviral resistance by characterizing anti-SIV innate immunity in the oral cavity of rhesus macaques. The long term goal of the proposed studies is to delineate the anti-HIV role of defensins, antiviral peptides now known to be present in saliva and expressed in epithelium of the oral cavity. Three human defensins were recently identified as anti-HIV factors produced by CD-8+ T cells from HIV-positive individuals who are long term non-progressors. We hypothesize that defensins conlribute to the anti-SIV/HW properties of saliva and to the innate resistance of oral mucosa, 2) that oral defensin expression develops postnatally, and 3) that the level of oral resistance to SIV in neonates may be augmented by topical application of one or more defensins. To test these hypotheses, we will pursue the following Specific Aims: ? Specific Aim 1 is to determine the level of alpha, beta,and theta-defensins present in saliva and/or expressed in the oral cavity of infant and adult rhesus macaques. ? Specific Aim 2 is to synthesize and/or recombinantly express specific alpha, beta, and theta-defensins confirmed (in Specific Aim 1) to be components of adult saliva and/or expressed in oral tissues. Peptides thus produced will be fully characterized and evaluated for their anti-SIV efficacy (Specific Aim 3), and will be used to produce anti-peptide immunologic reagents. ? Specific Aim 3 is to determine the anti-SIV and anti-HIV activities of oral alpha, beta,and theta-defensins in vitro. Anti-HW assays will be conducted with and without neonatal and adult saliva to ascertain the effect of this natural fluid on peptide activities. Combinations of peptides will also be analyzed to detect additive or synergistic pepfide-peptide interactions. ? Specific Aim 4 is to determine whether exogenous, topically administered defensin can alter the susceptibility to infection of neonatal rhesus macaques.